Add a check to silence an error when switching displays with xrandr.

[NicolasWebDev]

Hi,

When I dock/undock my laptop to an external display, I cal xrandr then I restart awesome.
In that case, I had the following error in my awesome logs:

2023-09-28 19:22:39 E: awesome: Error during a protected call: /home/sathors/.config/awesome/awesomewm-micky/init.lua:43: attempt to index a nil value (local 'client_under_mouse')
stack traceback:
    /home/sathors/.config/awesome/awesomewm-micky/init.lua:43: in function </home/sathors/.config/awesome/awesomewm-micky/init.lua:41>
    (...tail calls...)
    [C]: in function 'xpcall'
    /usr/share/awesome/lib/gears/protected_call.lua:36: in function </usr/share/awesome/lib/gears/protected_call.lua:35>
    (...tail calls...)
    /usr/share/awesome/lib/gears/timer.lua:198: in local 'func'
    /usr/share/awesome/lib/gears/object.lua:148: in function 'gears.object.emit_signal'
    [C]: in function 'xpcall'
    /usr/share/awesome/lib/gears/protected_call.lua:36: in function </usr/share/awesome/lib/gears/protected_call.lua:35>
    (...tail calls...)
    /usr/share/awesome/lib/gears/timer.lua:92: in function </usr/share/awesome/lib/gears/timer.lua:91>

To fix the error in that case, I added a simple check in the code to bail out if client_under_mouse is nil.

Maybe it is not the best way to fix the problem, I'm not sure, because my knowledge of lua scripting and of the awesome API is limited.

[basaran]

Not at all, it's the right way. Thank you for pointing it out. I actually had a similar fix on my local dev. I will create a dev branch soon to include this.